Add XML documentation for Java.Sql

The `Java.Sql` namespace contains **193** `To be added` placeholders in source XML documentation (excluding `docs\xml\index.xml`).

```powershell
rg -n -i --glob 'Java.Sql/**' --glob 'ns-Java.Sql.xml' 'to be added' docs\xml
```

## Update log

- 2026-09-10: Refreshed the placeholder scan from **206** to **193** (reduced by **13**). Related documentation PRs: [#551](https://github.com/dotnet/android-api-docs/pull/551), [#640](https://github.com/dotnet/android-api-docs/pull/640), [#644](https://github.com/dotnet/android-api-docs/pull/644).

Run the provided ripgrep command from the repository root to list the 193 remaining placeholders under docs\xml for Java.Sql, excluding docs\xml\index.xml. Review the matching XML documentation entries and replace each “To be added” placeholder with Java.Sql API documentation. Done means the scoped scan no longer reports those placeholders.

Vom Indexierungsmodell aus dem Issue-Text verfasst.